His time before the Slaughterhouse is unknown, but Crimson was one of the founding members of the Nine. 
Crimson and Winter were lovers, though the duration of this relationship is unknown as Bonesaw refers the couples time together as "brief" as crimson died shortly after. When cloning the pair Bonesaw took the time to replicate their relationship into their clones, but whether this is an indicator of how strong the relationship was or if Bonesaw was giving it extra weight due to her persona is unknown.
Crimson powers up into a super-strong form by consuming the blood of multiple victims, which he would augment with the use of a sword or other blade. After witnessing Crimson bulking up, Weaver refers to his power as, "...A little bit of a vampire [schtick], but the end result was more Mr. Hyde. Big, muscular, fueled by rage and impulse."
According to Weaver, "...his flesh would be engorged, purple-red, the veins would be standing out. He’d be as hard as iron, strong." 
In addition to his aforementioned relationship with Winter, their powers worked quite well together. According to Weaver, Winter would use her aura to capture victims for Crimson to feed on, at which time he would take to the front lines and draw fire from her, allowing her to support from range and negating the worry of friendly fire as he would be immune to her munitions.
There were ten of each in various glass chambers. The original members. - Excerpt from Interlude 25
↑Winter, white-haired, with white irises edged in black, nude, her eyes peering. Madeline’s eyes, Riley thought. Winter would need guns, of course.
Crimson, Winter’s brief-lived lover. Riley had taken the time to program their relationship into them. Crimson had been one of the first members in the group, Winter one of the more recent ones to die. Winter had been followed by Hatchet Face -there he was, over there, nine of them- and Hatchet Face had been followed by Cherish. - Excerpt from Interlude 25
↑The basement of the same building. Winter, Crimson, and their hostages. Some would be the ones from Killington. Others were ones that had fallen into the sway of Winter’s torpor. Crimson was feeding on them.
His schtick was a little bit of a vampire one, but the end result was more Mr. Hyde. Big, muscular, fueled by rage and impulse.
↑Crimson made his way outside. His flesh would be engorged, purple-red, the veins would be standing out. He’d be as hard as iron, strong. His sword was as long as he was tall. I couldn’t get a good measure of its appearance or quality. - Excerpt from Sting 26.2
↑I was going to spell out a response, get further details, but my focus shifted as Winter caught sight of Golem and Crimson and advanced.
Her dynamic with Crimson was one of synergy. She captured people so he could feed. He was the front line so she could safely attack from range. She slowed down opponents so he could advance. He was immune to her munitions fire, in large part. - Excerpt from Sting 26.2